The present invention relates to a suspension, a head gimbal assembly, and a method of manufacturing a head gimbal assembly. In particular, the present invention is concerned with holding a head slider on a suspension.
Data storage devices using various types of media such as optical disks and magnetic tapes are known in the art. Among them, hard disk drives (hereinafter referred to as HDDs) have become popular as storage devices for computers to such an extent that they are one type of the storage devices indispensable for today's computers. Further, not limited to computer systems, HDDs are expanding more and more in application because of their excellent characteristics. For example, HDDs are used for moving picture recording/reproducing devices, car navigation systems, cellular phones, and removable memories for use in digital cameras.
The HDD includes a magnetic disk for storing data and a head slider for making access to the magnetic disk. The head slider includes a head element portion which reads and/or writes data from and/or to the magnetic disk and a slider with the head element portion formed thereon. The head element portion includes a write element which converts an electric signal to a magnetic field in accordance with data written to the magnetic disk and/or a read element which converts a magnetic field provided from the magnetic disk into an electric signal. The HDD further includes an actuator for moving the head slider to a desired position over the magnetic disk. The actuator is driven by a voice coil motor (VCM) and pivots about a pivot shaft to move the head slider radially over the rotating magnetic disk. Thus, the head element portion makes access to a desired track formed on the magnetic disk, whereby it is possible to perform data read/write processing.
The actuator includes an elastic suspension and the head slider is fixed to the suspension with an adhesive. Pressure based on the viscosity of air present between an ABS (Air Bearing Surface) of the head opposed to the magnetic disk and the rotating magnetic disk counteracts pressure applied in the direction of the magnetic disk by the suspension. This enables the head to fly over the magnetic disk at a certain gap.
An assembly of the head slider and the suspension is designated as a head gimbal assembly (HGA). FIG. 8 shows an HGA by way of example as viewed from the recording surface side of the magnetic disk. As shown in FIG. 8, the HGA 400 includes a head slider 401, a suspension 402 and a trace 403 as transmission wiring. The suspension 402 includes flexible gimbals 404 which holds the head slider 401 on the side opposed to the magnetic disk, as well as a load beam 405 and a mounting plate 406 both holding the head slider 401 on the side opposed to the magnetic disk. The illustrated HGA 400 is of a load/unload type and is provided at a front end of the load beam 405 with a tab 407 for unloading to a ramp mechanism. The head slider 401 is formed at its front surface (on the tab side) with plural terminals connected to the head element portion. Those terminals and the wiring lines of the trace 403 are connected together, for example, by soldering or gold ball bonding.
The manufacture of an HGA involves a test called a dynamic electric test (DET). In the DET, an HGA is set in a testing device, actual read/write processing is performed on a rotating magnetic disk, and then the head slider is evaluated for flying characteristics and read/write characteristics. An HGA that satisfies required specifications in the DET advances to the next manufacturing step, while an HGA regarded as rejection is discharged to waste. Thus, when the head slider does not satisfy the required specifications, the suspension with the head slider fixed thereto is also discharged to waste, which is a loss in the manufacture of the HGA.
To eliminate such a loss of the suspension in the HGA manufacture, a DET device has been proposed which permits mounting and removal of the head slider (see, for example, Patent Literature 1: Japanese Patent Laid-open No. 2004-86976). By using such a testing device for the head slider alone, it is possible to conduct the DET before mounting of the head slider onto the suspension and hence to prevent a loss of the suspension caused by the defective head slider.
In addition, a technique has been proposed which improves the adhesive for fixing the head slider to the suspension and thereby permits removal of a defective head slider from the suspension (see, for example, Patent Literature 2: Japanese Patent Laid-open No. 2002-150734). The DET evaluates the head slider for characteristics in the state of the HGA. The adhesive is in a state of gel at low temperatures, assumes a melted state at high temperatures and is cured at still higher temperatures. The head slider and the suspension are fixed together temporarily with the adhesive that is in a state of gel. In this state, the DET is performed. If the head slider is defective, the adhesive is heated into a melted state, in which the head slider is removed from the suspension. If the head slider satisfies the required specifications, the adhesive is cured by heating to effect an external connection between the head slider and the suspension.